The overall "softness" of your image stems not from the development, IMO. At the distances involved, you have a very short plane of sharp focus. If your Jupie 9 was set wide open, it would, thus, minimize the depth of field.
There may be an additional reason for softness if you were shooting wide open, as that lens does not show its real sharpness until stopped down a stop or two.
Plus you have a doggie that is not sitting absolutely still, I would venture.
If you print the neg, boost the contrast a bit and it will appear sharper. But I do not think you should be opting to blame the film developer--which at that dilution has a reputation for making "sharp appearing" negatives.
I have that lens myself--even use it on a Spotmatic F-- and find it a very good performer--wide open for softness in portraits when desired; and stopped down a few stops to sharpen things up.